We are testing 5 different types of salt (table salt, kosher salt, sea salt, Epsom salts, and rock salt) and their effect on the speed of melting ice blocks (against a control, of course). We are trying to figure out: (1) if it makes a difference whether we measure the runoff water in volume in a measuring cup or by mass on a balance or scale; and (2) if we need to set up the bowls to allow for real-time runoff of the melted ice/water in order to measure and compare the true melting effects of the different types of ice, or if it will be sufficient to pour off the runoff at designated intervals (I believe that if the ice sits in water too long, a lot of the salt could potentially dissolve into the water instead of continuing to work its melting magic on the ice blocks).

Project Question: My daughter and I are going to measure which type of salt melts ice the fastest (comparing table salt, kosher salt, sea salt, epsom salts, and rock salt to a control). 2 questions: (1) when we measure the amount of melt/water, is it important whether we measure by volume in a measuring cup or by mass on a balance or scale; and (see below)

Project Due Date: March 4.

Question #2: will it make a difference whether we have a way for the melted water/runoff to exit each ice bowl as it melts (and measure the collected runoff at designated intervals) or we pour off the water from each ice bowl at designated intervals?

This is very helpful. In terms of the runoff, do you think it is sufficient to pour off the runoff at designated intervals, or do you think it's important to find a way to siphon off the runoff on a real-time, ongoing basis?

Project Question: My daughter and I are going to measure which type of salt melts ice the fastest (comparing table salt, kosher salt, sea salt, epsom salts, and rock salt to a control). 2 questions: (1) when we measure the amount of melt/water, is it important whether we measure by volume in a measuring cup or by mass on a balance or scale; and (see below)

Project Due Date: March 4.

Question #2: will it make a difference whether we have a way for the melted water/runoff to exit each ice bowl as it melts (and measure the collected runoff at designated intervals) or we pour off the water from each ice bowl at designated intervals?

Since your experiment is testing the effect of different salts on the melting properties of ice. You are right to try and control the loss of salt, but also control the environment around the ice. From your post, you talk about a block of ice, so I'm guessing that you might end up with a fair amount of water that may actually cover part of the ice sample. In this case, water can actually act as insulation. The cool water at a lower temp than the surrounding air, prevents further melting and reduces the surfaced area of the ice exposed to the air. If you were going to periodically remove the water, you would have to make sure you did it often and in the same way, time frame, for each sample to ensure the conditions of the test are as close to the same for all samples, save your independent variable, the salt. So my advice is to place the ice samples in identical containers with holes in the bottom...something like a colander...so liquid water can run out. Under this, place something that can collect the runoff.

As for measurement, it would be best to use the initial mass of the ice and then the mass of the water and remaining ice. You can then make direct comparisons and calculate the percentage of ice melted, ice remaining.

For additional ideas and information, reference this project on science buddies that is very similar to the one you are conducting:

You'll notice that in this experiment, you only pour off the melt at the end of the experiment, but this one uses single cubes of ice, the amount of water is unlikely to cause significant error in conditions.

Project Question: "To explain all nature is too difficult a task for any one man. 'Tis much better to do a little with certainty and leave the rest for others that come after you, than to explain all things by conjecture without making sure of anything." - Sir Isaac Newton